In recent years, contamination with mold and bacteria in hospitals and food factories has become a problem. Mold and bacteria grow significantly especially in the rainy season when humidity is high and condensation occurs. Therefore, walls and other parts in factories are coated with mold-preventing, antibacterial paint to inhibit the growth of mold and bacteria. Air conditioning equipment has an air filter which has been subjected to mold-preventing, antibacterial treatment, which captures dust, mold, and bacteria floating in the air to purify the air.
An air filter is made of a filter material such as glass fiber, paper, or nonwoven fabric, and the material is pleated to increase the filtration area and filtration property. A filter material having low rigidity such as melt blown nonwoven fabric, which has a poor pleat-retaining property. Therefore usually a filter material is bonded with a rigid nonwoven fabric for reinforcement and the bonded filter material is pleated.
For example, Patent Document 1 discloses a dust collecting filter (air cleaning filter) for an air conditioner, which is loaded with a mold-preventing agent, an antibacterial agent and an antiviral agent, wherein the mold-preventing agent includes an organic nitrogen-based compound, a sulfur-based compound, an organic acid ester, an organic iodine-based compound and an imidazole compound, and wherein tea extract may be used as the antibacterial and antiviral agents.
As in Patent Document 1, Patent Document 2 also discloses a dust collecting filter (air cleaning filter) for an air conditioner, which is loaded with a mold-preventing agent, an antibacterial agent, and an antiviral agent, wherein the mold-preventing agent includes an organic nitrogen-based compound, a sulfur-based compound, an organic acid ester, an organic iodine-based compound, an imidazole compound, a vegetable essential oil, a benzole compound and so on, and wherein a p-benzoquinone derivative from bamboo extract may be used as the antibacterial and antiviral agents.
However, conventionally and commonly used mold-preventing agents and antibacterial agents involve a problem that these agents cannot achieve their effects sufficiently when they are under dry condition.
Another problem with conventionally and commonly used mold-preventing agents or antibacterial agents is that long-term use of these agents may change mold and bacteria to wild-type microorganisms (fungi or bacteria) and bacteria having resistance to these agents, making these agents less effective. The mold-preventing agent includes an organic nitrogen-based compound, a sulfur-based compound, an organic acid ester, an organic iodine-based compound, an imidazole compound, and the antibacterial agent includes a silver-based compound, a zinc-based compound, an alcohol-based compound, a phenol-based compound, a quaternary ammonium salt, benzoates, hydrogen peroxide, cresol, chlorhexidine, Irgasan, aldehydes and sorbic acid.